236 constant weight shall be performed at a temperature of 140 ± 5 degrees F. 303- 3.03 Finishing: The final layer of subbase or base shall be finished with equipment capable of shaping and grading the finish surface within the tolerances specified herein. The f inished surface of aggregate subbase or aggregate base shall not vary from the grades established by the Engineer by more than ± 0.04 feet. The compacted layers of aggregate subbase and aggregate base shall be maintained in a condition satisfactory to receive any subsequent subbase, base, or surfacing material or traffic, when so required. Areas not within the allowable tolerance shall be corrected by scarifying, placing additional material, re- mixing, reshaping , and re- compacting to the specified density a nd surface tolerance. 303- 4 Method of Measurement: The quantity of aggregate subbase and aggregate base will be calculated by the cubic yard in place, using plan dimensions. 303- 5 Basis of Payment: The accepted quantities of aggregate subbase and aggregate base, measured as provided above, will be paid for at the contract unit price per cubic yard for the class or classes involved, complete in place. 304- 1 Description: The work under this section shall consist of furnishing and mixing aggregate, cement , and water, and spreading, compacting , and curing the mixture in accordance with the details shown on the project plans and the requirements of these specifications. 304- 2 Materials: 304- 2.01 Aggregate: Aggregate shall conform to the requirements of Subsection 303- 2 of the specifications for Class 2 aggregate, unless otherwise specified in the Special Provisions. TABLE OF CONTENTS INDEX 237 304- 2.02 Hydraulic Cement and Water: Hydraulic cement and water shall conform to the requirements of Subsection 1006- 2 of th e specifications. 304- 2.03 Bituminous Material for Curing Seal: Bituminous material for curing seal shall be Emulsified Asphalt Grade SS-1 conforming to the requirements of Section 1005 of the specifications. 304- 2.04 Mix Design: The contractor shall determine the mix proportions and shall furnish cement treated base conforming to the requirements specified herein. The job- mix design with the supporting test results shall be submitted to the Engineer and the Engineer's approval shall be obtained prior to incorporating any of the material into the work. The brand of cement and the location of the aggregate source shall be included with the job mix design data. A new mix design shall be submitted for approval any time the contractor requests a change in materials or proportioning of the materials from that given in the approved mix designs. Unless otherwise specified, cement treated base shall contain no less than 165 pounds of hydraulic cement per cubic yard, and it shall attain a minimum compressive strength of 500 pounds per square inch at seven days. 304- 3 Construction Requirements: 304- 3.01 Preparation of Subgrade: Cement treated base shall be placed on a prepared subgrade which shall have been constructed in accordance with the surface finish and grade tolerance requirements specified for the subgrade material involved. The subgrade shall be free of loose or extraneous material and maintained in an acceptable condition throughout the treatment operation. Any soft or yielding areas of the subgrade shall be corrected prior to placement of cement treated base. 304- 3.02 Mixing :
Aggregate and cement for cement treated base shall be proportioned and mixed in a central mixing plant, unless otherwise specified. The plant shall be either the batch- mixing type using revolving blade or rotary drum mixers, or the continuous mixing type. The aggregate and cement may be proportioned either by weight or by volume. TABLE OF CONTENTS INDEX 238 Water shall be proportioned by weight or volume and there shall be means by which the Engineer may readily verify the amount of water required per batch or the rate of water flow required for continuous mixing. The time of the addition of water or the points at which it is introduced into the mixer shall be as approved by the Engineer. The moisture content of the completed mixture shall be uniform and within 2 percentage points of the optimum at the point of delivery to the work. The optimum moisture content will be determined in accordance with the requirements of the applicable test methods of the ADOT Materials Testing Manual, as directed and approved by the Engineer. The cement shall be added in such a manner that it is uniformly distributed throughout the aggregate during the mixing operation. There shall be safe, convenient facilities for sampling the cement in the supply line to the weigh hopper or pugmill. The charge in the batch mixer or the rate of feed to the continuous mixer shall not exceed that which will permit complete mixing of all of the mix material.
The mixer shall be equipped with a sufficient number of paddles of a type and arrangement which will produce a uniformly mixed batch. The mixer shall be equipped with an accurate timing device which will indicate by a definite audible or vis ual signal the expiration of the mixing period. The time of mixing a batch shall begin after all ingredients are in the mixer and shall end when the mixer is half emptied. Mixing shall continue until a homogeneous mixture of uniformly distributed and properly coated aggregate of unchanging appearance is produced. The time of the mixing shall not be less than 30 seconds. The batch- mixing plant shall be equipped with sampling facilities as approved by the Engineer. The sampling facilities shall allow for t he easy and safe collection of representative samples of aggregate and cement treated base mixture.
Aggregate shall be drawn from the storage facility by a feeder or feeders which will continuously supply the correct amount of aggregate in proportion to the cement. A control system shall be provided that will automatically close down the plant when the material in any storage facility approaches the strike- off capacity of the feed gate. The plant will not be permitted to operate unless this automatic control system is in good working condition. TABLE OF CONTENTS INDEX 239 The feeder for the aggregate shall be mechanically or electrically driven. Continuous mix plants shall be equipped with sampling facilities approved by the Engineer. The sampling facilities shall allow for the easy and safe collection of representative samples of aggregate and cement treated base mixture. The cement feeder and the aggregate feeders shall be equipped with devices by which the rate of feed can be accurately determined while the plant is in full operation.
Mixed material shall be transported from the plant to the roadway in approved vehicles and spread on a moistened subgrade in a uniform layer for the full width of the base under construction. Mixed material may be placed in partial widths as approved by the Engineer. Spreading shall be accomplished with approved spreader boxes or finishing machines or motor graders. If the Engineer approves the use of one spreader operating alternately on two or more lanes, not more than 30 minutes shall elapse between the time of placing the material in adjacent lanes at any location. The material shall be spread full depth in one pass unless otherwise specified. Cement treated base shall not be mixed or placed while the air temperature is below 40 degrees F in the shade or when conditions indicate that the temperature may fall below 40 degrees F within 24 hours. Cement treated base shall not be placed on frozen subgrade or mixed when the aggregate is frozen. 304- 3.03 Compacting and Finishing: Initial compaction shall begin immediately after spreading. Successive passes of compacting equipment shall overlap the previous adjacent pass by at least 25 percent of its width. Following initial compaction and before final compaction, the treated material shall be trimmed by blading with a motor grader or a planing machine to obtain surface in reasonably close conformity with the lines, grades, and cross- sections established or shown on the project plans. Extreme care shall be exercised by the contract or during the trimming operation so that no more material than is necessary is disturbed and so that the trimming operation can be completed as quickly as possible. Trimmed material shall be wasted if so directed. Compaction shall proceed without interruption, except as stated above, to achieve at least 100 percent of maximum density as determined in accordance with the requirements of the applicable test methods of the ADOT Materials Testing Manual, as directed and approved by the Engineer. TABLE OF CONTENTS INDEX 240 The finished surface of cement treated base shall be uniform and shall not deviate at any point more than 0.03 feet from the bottom of a 10- foot straightedge laid in any direction. The surface of the finished cement treated base shall not vary more than 0.04 feet.above or below the grade established by the Engineer. The surface shall be kept moist at all times until the curing seal is applied. 304- 3.04 Operation Time Requirement: Not more than two hours shall elapse between the time water is added to the aggregate and cement, and the time of completion of initial compaction prior to trimming. Not more than 2.5 hours shall elapse between the time water is added to the aggregate and cement and the time of completion of final compaction. 304- 3.05 Construction Joints: At th e end of each day's work or when cement treated base operations are delayed or stopped for more than two hours, a construction joint shall be made in thoroughly compacted material. The joint shall be normal to the center line of the roadbed and have a ver tical face. Additional mixture shall not be placed until the construction joint has been approved by the Engineer. When partial -width construction of cement treated base is allowed and when the material has been finally compacted more than one hour, a longitudinal joint shall be constructed by cutting back into the previously placed material to a point where it meets the proper line and grade, and trimmed to a true vertical face which is free of any loose or shattered material. Trimmed material shall be disposed of. The face of transverse and longitudinal construction joints shall be moistened prior to placement of the adjacent base material. 304- 3.06 Curing Seal: After final compaction, the cement treated base shall be covered with a bituminous curing seal, applied uniformly to the surface at an approximate rate of 0.15 gallons per square yard. The curing seal shall be applied on the same day that final compaction is performed and as soon after the compaction as is practicable. After the curing seal has been applied, the cement treated base shall be kept free of traffic for a period of at least three days. Only light construction traffic will be allowed from the fourth through the seventh day after the curing seal has been placed. Subsequent subbase, base, or pavement course shall be placed within 10 days after the curing seal is applied. TABLE OF CONTENTS INDEX 241 Any damage to the curing seal or the cement treated base shall be promptly repaired by the contractor, at its expense and as directed by the Engineer. When the project plans call for 4 or more inches of aggregate base over the cement treated base, the aggregate base may be used as the curing seal in lieu of a bituminous curing seal. The aggregate base shall be kept moist for 72 hours after placement. The section may be opened to traffic immediately after placement and compaction of the aggregate base. 304- 3.07 Cement Treated Base Strength Tests: Samples for strength tests will be taken at random for each lot of production. A lot shall be considered to be the production during one shift. Each lot shall be represented by five random samples, each sampled and tested in accordance with Arizona Test Method 241. The mean value of the sample strengths will be reported to the nearest pound per square inch. 304- 4 Method of Measurement: Cement treated base will be measured by the ton. 304- 5 Basis of Payment: The accepted quantities of cement treated base, measured as provided above, will be paid for at the contract unit price for the cement treated base mixture, complete in place, including bituminous curing seal when required, except that an adjustment will be made to the unit price paid for any lot represented by the mean value of the seven- day compressive strengths as shown in Table 304- 1. TABLE 304 -1 Mean Compressive Strength Unit Price Adjustment (Pounds per square inch) (dollars per ton) 500 or more 0 450 to 499 - 1.50 400 to 449 - 3.25 350 to 399 - 5.00 Less than 350 * - 7.00 Note:
*Material represented by lots attaining seven- day compressive strengths with a mean value less than 350 pounds per square inch will be evaluated as to acceptance. The Engineer will determine if the material can be left in place. Cement -treated base allowed to remain in place will be subject to the unit price adjustment. Cement -treated base not allowed to remain in place shall be replaced at no additional cost to the Department.
TABLE OF CONTENTS INDEX 242 SECTION 305 LEAN CONCRETE BASE : 305- 1 Description: The work under this section shall consist of furnishing all materials and constructing a lean concrete base in accordance with the details shown on the project plans and the requirements of these specifications. Lean concrete base shall consist of a mixture of aggregate, hydraulic cement, water , and admixtures. 305- 2 Materials: 305- 2.01 Hydr aulic Cement and Water: Hydraulic cement and water shall conform to the requirements of Subsection 1006- 2 of the specifications. 305- 2.02 Aggregate: At the option of the contractor, the aggregate for lean concrete b ase shall be either Class 2 aggregate base material conforming to the requirements of Subsection 303- 2 of the specifications or a combination of fine and coarse aggregate for Portland cement concrete conforming to the requirements of Subsection 1006- 2.03 of the specifications. When Class 2 aggregate base material is used, it shall have a minimum sand equivalent value of not less than 50 when tested in accordance with the requirements of AASHTO T 176, and the plasticity index requirements presented in Subsection 303- 2 of the specifications will not apply. When a combination of fine and coarse aggregate is used, the coarse aggregate shall be Standard Size Designation No. 57 conforming to the requirements of AASHTO M 43. Fine aggregate shall have a minimum sand equivalent of not less than 50 when tested in accordance with the requirements of AASHTO T 176. 305- 2.03 Admixtures: Admixtures shall conform to the requirements of Subsection 1006- 2.04 of the specifications. 305- 2.04 Curing Compound: Curing compound shall be Type 2, Class A liquid membrane- forming compound conforming to the requirements of Subsection 1006- 6.01(C) of the specifications. TABLE OF CONTENTS INDEX 243 305- 3 Construction Requirements: 305- 3.01 Preparation of Subgrade, Subbase , or Base: Lean concrete base shall be placed on a prepared subgrade, subbase, or base which shall have been constructed in accordance with the surface finish and grade tolerance requirements specified for the material involved. The subgrade, subbase, or base shall be free of loose or extraneous material, kept uniformly moist immediately prior to placement of lean concrete base and maintained in an acceptable condition throughout the placement operation. Any soft or yielding area of the subgrade shall be corrected prior to placement of lean concrete base. 305- 3.02 Forming: Lean concrete base shall be constructed with slip- form equipment. Forming shall conform to the requirements of Subsections 401- 3.03(A), 401- 3.03(B), and 401- 3.03(C) of the specifications . 305- 3.03 Proportioning:
The contractor shall determine the mix proportions and shall furnish lean concrete base which shall contain not less than 275 pounds of hydraulic cement per cubic yard, however, the amount of cement in the mix may be reduced when fly ash is added as hereinafter specified. The lean concrete base shall attain a minimum compressive strength of 500 pounds per square inch at seven days. The contractor shall submit a complete solid- volume mix design to the Engineer for review prior to incorporating the proposed mix into the work. Mix designs submitted for review shall include the weights and volumes of all ingredients; the brand, type and source of hydraulic cement and admixtures; the aggregate base or the coarse aggregate size number designation; the source of aggregate; the specific gravities of all ingredients; and a code number to identify th e mix design. The contractor may submit mix designs from previous or concurrent projects. The contractor shall make no changes in the mix designs or code numbers without the review of the Engineer. A new mix design shall be submitted for the Engineer's r eview any time the contractor proposes a change in materials or material proportions. The contractor shall prepare trial batches of lean concrete base for each mix design. The number of trial batches required will be established by the Engineer and the Engineer may waive the requirements for trial batches at any time. The contractor shall prepare trial batches using TABLE OF CONTENTS INDEX 244 materials, mixing equipment, procedures and batch sizes which are the same as those to be used in the work. The Engineer will take test samples from the trial batches. When test results indicate the proposed mix will not meet the specified compressive strength requirements, the contractor shall submit a new mix design for review. In no case will the Engineer's review or test of a mix design relieve the contractor of the responsibility to provide lean concrete base with the specified properties or material contents.
Cement, water , and aggregate shall be proportioned in accordance with the requirements of Subsections 1006- 4.02(A), (B) and (C) of the specifications.
Admixtures shall be proportioned in accordance with the requirements of Subsection 1006 -4.02(D) of the specifications. Air-entraining admixtures will be required for lean concrete base placed at elevations above 3,000 feet. The amount of entrained air in the lean concrete mixture shall not be less than 4 percent, nor more than 7 percent by volume. At elevations below 3,000 feet, air -entraining admixtures may be used at the option of the contractor; however, the amount of entrained air in the lean concrete mixture shall not exceed 7 percent by volume. An approved water reducing admixture shall be used. A fly ash admixture may be used at the option of t he contractor only when Portland cement is used. A maximum of 20 percent, by weight, of the Portland cement may be replaced with fly ash. A minimum of 1.2 pounds of fly ash shall replace each pound of Portland cement. 305- 3.04 Mixing : Mixing shall be performed in accordance with the requirements of Subsection 1006- 4.03 of the specifications. 305- 3.05 Consistency: The contractor shall furnish lean concrete base having a slump of 4.5 inches or less. Lean concrete base that fails to conform to this consistency requirement will be rejected. Tests for consistency will be performed in accordance with the requirements of AASHTO T 119. TABLE OF CONTENTS INDEX 245 305- 3.06 Weather Limitations: Lean concrete base shall be constructed in accordance with the weather limitations of Subsection 1006- 5 of the specifications. 305- 3.07 Joints: There shall be no longitudinal or transverse weakened plane joints in lean concrete base. Transverse construction joints shall be constructed normal to center line of the pavement at the end of each day's production and during other work interruptions as directed by the Engineer. When Portland cement concrete pavement is to be placed over lean concrete base, longitudinal construction joints in the lean concrete base shall be at least 2 feet from any subsequent longitudinal joint in the Portland cement concrete pavement. 305- 3.08 Placing and Finishing: Lean concrete base shall be placed and fini shed in accordance with the applicable requirements of Subsection 401- 3.04 of the specifications except that Subsection 401- 3.04(F) of the specifications, is not applicable. Lean concrete base may be placed either for the full width in a single pass or in two or more passes, provided that each pass is a minimum of 12 feet wide wherever possible. Longitudinal construction joints between passes shall conform to the requirements of Subsection 305- 3.07 of the specifications. The surface of the lean concrete base shall be finished to a smooth floated surface and the surface plane shall not vary by more than 1/8 inch in any direction when measured with a 10- foot straightedge, nor vary by more than 1/4 inch across any construction joint. 305- 3.09 Curing: Curing of lean concrete base shall begin immediately after surface finishing operations. Liquid membrane- forming compound shall be applied to the surface and sides of the lean concrete base at a rate of not less than one gallon per 100 square feet. The curing compound container shall be equipped with a calibrated sight glass for verification of quantities used. 305- 3.10 Production Lot: The compressive strength and thickness of lean concrete base will be evaluated for each lot of production. A lot shall consist of 4,000 square yards, or fraction thereof, of continuously placed lean concrete base, on a daily basis. TABLE OF CONTENTS INDEX 246 305- 3.11 Compressive St rength: The minimum average compressive strength of lean concrete base shall be 500 pounds per square inch for each lot at seven days. Each lot shall be represented by four random samples. A strength test will consist of the average strength of two cylinders prepared with material taken from a single load of lean concrete base. If any cylinder should show obvious evidence of improper sampling, molding, or testing, it will be discarded and the strength test will consist of the strength of the remaining cylinder. All test cylinders will be prepared in accordance with the requirements of AASHTO T 23. Testing for compressive strength will be performed in accordance with the requirements of Arizona Test Method 314. The mean value of the four compressive strength tests will be reported to the nearest pound per square inch. The unit price paid for the lean concrete base in that lot will be adjusted in accordance with the provisions of Subsection 305- 5 of the specifications. 305- 3.12 Opening to T raffic : No traffic or equipment will be permitted on lean concrete base until the material has attained the specified seven -day compressive strength. However, when lean concrete base is to be placed adjacent t o previously constructed lean concrete base, the paver and work bridges required for completing the new width will be permitted on the lean concrete base 72 hours after placement. The contractor shall schedule its operations and route its equipment such that the base is subjected to minimal traffic. When it is necessary for construction traffic to travel on lean concrete base which has attained the specified compressive strength, the traffic shall comply with all legal load restrictions applicable to traff ic on state highways. No overloaded vehicles will be permitted to travel on the lean concrete base under any circumstances. Damage to the curing compound or to the lean concrete base which occurs as a result of the contractor's construction activities shall be promptly repaired by the contractor at no additional cost to the Department, when so directed by the Engineer. 305- 3.13 Lean Concrete Base Thickness: Lean concrete base shall be constructed to the specified thickness. Tolerances allowed for base and subgrade construction and other provisions of the Specifications which may affect thickness shall not be construed to modify the lean concrete base thickness requirements. To determine thickness acceptability, the cont ractor shall drill 4 inch minimum diameter cores at the locations specified by the Engineer. The Engineer will determine average core thickness in accordance with the provisions of AASHTO T 148, except that the measurements will be TABLE OF CONTENTS INDEX 247 made to the nearest thousandth of an inch, and the average of the measurements will be reported to the nearest hundredth of an inch. When calculating average core thicknesses, cores which exceed the specified thickness by more than 0.25 inches will be considered to have the speci fied thickness plus 0.25 inches. The Engineer may make field thickness measurements in lieu of measurements in accordance with AASHTO T 148 when an initial core taken from any unit exceeds the specified thickness; however, when the initial core is less than the specified thickness or when there is any question as to the unit thickness, thicknesses will be determined in accordance with AASHTO T 148. To determine the acceptability of each lot of lean concrete base, the following procedures will be followed:
of the core is not deficient by more than 0.25 inches, the thickness of the lean concrete base in that lot will be considered acceptable;
0.25 inches, but less than or equal to 0.75 inches, two additional cores shall be drilled within that lot and the thickness of the three cores will be averaged. The average of the three cores will be used to determine acceptability, and the unit price paid for the Lean Concrete Base in that lot will be adjusted as specified in Subsection 305 -5 of the specifications; and
cores shall be drilled at intervals not to exceed 10 feet in each direction from the deficient core, parallel to the roadway center line, until one core is obtained in each direction which is not deficient by more than 0.75 inches. The lean concrete base between these two cores will be evaluated separately from the balance of the lean concrete base in that lot, and unless otherwise directed by the Engineer, shall be removed and replaced with lean concrete base of the specified thickness. At all locations where cores have been drilled, the resulting holes shall be filled with lean concrete base or other similar material as approved by the Engineer. 305- 4 Method of Measurement: Lean concrete base will be measured by the square yard. TABLE OF CONTENTS INDEX 248 305- 5 Basis of Payment: The accepted quantities of lean concrete base, measured as provided above, will be paid for at the contract unit price, complete in place, except that an adjustment to the nearest cent in the contract unit price will be made in accordance with Table 305- 1 and Table 305- 2, when either the quality of concrete represented by the mean value of the four compressive strength tests is less than the specified seven day compressive strength or when the average lengths of cores indicates deficiencies in thickness by more than 0.25 inches, but less than or equal to 0.75 inches. Where a deficiency exists in both the average length of cores and the average compressive strength, the amount of the contract unit price allowed will be the appropriate percentage of contract unit price allowed from Table 305 1 less the unit price adjustment from Table 305 2. TABLE 305 -1 ADJUSTMENT IN CONTRACT UNIT PRICE FOR DEFICIENCY IN THICKNESS OF LEAN CONCRETE BASE Average Core Length, Less Than Specified Thickness: Inches Unit Price Allowed: Percent of Contrac t 0.00 to 0.25 100 0.26 to 0.35 93 0.36 to 0.45 85 0.46 to 0.55 75 0.56 to 0.75 50 Greater than 0.75* 25 Note:
*Material represented by cores deficient by more than 0.75 inches in thickness and/or represented by lots attaining seven- day compressive strengths with the mean value of the four compressive strength tests less than 350 pounds per square inch will be evaluated as to acceptance. The Engineer will determine if the material can be left in place. Lean concrete base allowed to remain in place will be subject to the unit price adjustments presented in Tables 305- 1 and 305-
shall be removed and replaced at no additional cost to the Department.
TABLE 305 -2 ADJUSTMENT IN CONTRACT UNIT PRICE FOR DEFICIENCY IN COMPRESSIVE STRENGTH OF LEAN CONCRETE BASE Mean Compressive Strength (pounds per square inch) Unit Price Adjustment ** (dollars per square yard) 500 or more 0 450 to 499 - 1.50 400 to 449 - 3.25 350 to 399 - 5.00 Less than 350 * - 7.00 TABLE OF CONTENTS INDEX